People rely on absorbent articles to help participate in and enjoy their daily activities.
Absorbent articles, including adult incontinence articles and diapers, are generally manufactured by combining a substantially liquid-permeable topsheet; a substantially liquid-impermeable backsheet attached to the topsheet; and an absorbent core located between the topsheet and the backsheet. When the article is worn, the liquid-permeable topsheet is positioned next to the body of the wearer. The topsheet allows passage of bodily fluids into the absorbent core. The liquid-impermeable backsheet helps prevent leakage of fluids held in the absorbent core. The absorbent core is designed to have desirable physical properties, e.g. a high absorbent capacity and high absorption rate, so that bodily fluids can be transported from the skin of the wearer into the disposable absorbent article.
The topsheet, backsheet, absorbent core, and other components of an absorbent structure or product may comprise discrete layers or nonlayered shapes and configurations. Furthermore, these components or pieces may be coextensive or non-coextensive, depending on the requirements of the product. Generally each of the individual components or pieces is arranged so that it is in intimate contact along at least a portion of its boundary with at least one other adjacent component or piece of the absorbent article or structure. Typically each component or piece is connected to an adjacent portion of the absorbent structure by a suitable bonding and/or fiber entanglement mechanism, such as ultrasonic or adhesive bonding, or mechanical or hydraulic needling.
Thus, as an absorbent structure or product is made, it generally undergoes a number of different steps in which components or pieces are connected to one another. For example, portions of the topsheet and backsheet typically are bonded together. Also, to the extent the absorbent structure or product incorporates elastomeric regions such as elasticized waistbands or elasticized leg bands or leg cuffs, elastic strands or elastic ribbons are typically bonded to a portion of one or more base materials, substrates, or webs.
If an adhesive is used to attach a portion of one component or piece to a portion of another component or piece to form a composite, the adhesive may be exposed to ultrasonic energy in subsequent processing steps if part or all of the composite passes through ultrasonic-treating equipment. The ultrasonic energy may cause the adhesive to flow. This in turn may lead to build up or accretion of the adhesive on parts of the ultrasonic-treating equipment if the adhesive penetrates through some or all of the composite, between separate layers of the composite if the composite is a laminate, or both. This build up or accretion may decrease performance of the ultrasonic-treating equipment, and may lead to increased down time of the production machine.
What is needed is a composite and absorbent article comprising an adhesive that is less susceptible to building up or accreting on the surfaces of ultrasonic-treating equipment, and a method of making such a composite and article.
We have found that an adhesive is less likely to build up or accrete on the surfaces of ultrasonic-treating equipment if the adhesive has a capillary-viscosity value of about 7 Pascal seconds (hereinafter referred to as xe2x80x9cPas.secxe2x80x9d) or greater and a Shore-OO-Hardness value of about 65 or greater, and more particularly a capillary-viscosity value of about 9 Pas.sec or greater and a Shore-OO-Hardness value of about 90 or greater. As discussed below, the recited capillary viscosities are reported as real (rather than apparent) viscosities corresponding to a shear rate of 5000 secondsxe2x88x921. Where necessary, these recited viscosities were obtained by interpolation. Shore-OO-Hardness values are reported in units of durometer.
Accordingly, one version of the invention is directed to a composite comprising a first piece and a second piece, a portion of the first piece being bonded to a portion of the second piece using an adhesive composition having a capillary-viscosity value of about 7 Pas.sec or greater and a Shore-OO-Hardness value of about 65 or greater, wherein the relative accretion value is less than about 1, and more particularly less than about 0.5. As defined below, xe2x80x9crelative accretion valuexe2x80x9d is the mass of an adhesive having features of the present invention that accretes or builds up (alone or in combination with other materials) on surfaces of ultrasonic-treating equipment divided by the mass of another adhesive that accretes or builds up (alone or in combination with other materials) on surfaces of ultrasonic-treating equipment (under the same conditions and using the same equipment, with the difference being the identity of the adhesive used). The identity of the adhesive corresponding to the accretion value appearing in the denominator of the relative accretion value is that of a conventional adhesive used to bond pieces together when making a composite. In the examples below, the identity of the adhesive corresponding to the accretion value appearing in the denominator is a hot-melt adhesive composition available under the alpha-numeric designator H2096 from Bostik Findley (formerly known as Ato Findley), a business having offices in Wauwatosa, Wis. It should be understood that the relative accretion index serves to quantify a feature of composites and absorbent products of the present invention: when composites or absorbent products of the present invention are processed by ultrasonic-treating equipment, there is less buildup or accretion of adhesive and other materials on the surfaces of the ultrasonic-treating equipment compared to the buildup or accretion that occurs when processing composites or absorbent products incorporating conventional adhesive compositions.
In some versions of the invention, a first piece is not attached to a second piece to form a composite, but instead a single piece is folded over and attached to itself using an adhesive composition having the above-recited properties.
Another version of the invention is directed to a composite comprising a first piece and a second piece, a portion of the first piece being bonded to a portion of the second piece using an adhesive composition having a capillary-viscosity value of about 9 Pas.sec or greater and a Shore-OO-Hardness value of about 90 or greater, wherein the relative accretion value is less than about 0.1, and more particularly less than about 0.05. In some versions of the invention, a first piece is not attached to a second piece to form a composite, but instead a single piece is folded over and attached to itself using an adhesive composition having the above-recited properties.
In another aspect, the invention is directed to a composite having a creep-resistance value of about 30% or greater, specifically about 40% or greater, and particularly about 50% or greater, the composite comprising: a first piece and a second piece; at least one elastic strand or ribbon; and an adhesive composition binding at least a portion of each strand or ribbon to a portion of the first piece and a portion of the second piece, the adhesive composition having a capillary-viscosity value of about 7 Pas.sec or greater and a Shore-OO-Hardness value of about 65 or greater, wherein the relative accretion value is less than about 1, and more particularly less than about 0.5. In some versions of the invention, the elastic strand or ribbon is not attached to a first piece and a second piece to form a composite, but instead is attached to, and enclosed by, a single piece (e.g., by folding over a portion of the single piece over the elastic strand or ribbon to form a composite). xe2x80x9cCreep-resistancexe2x80x9d refers to the elastic-strand (or elastic ribbon) holding power of a particular system for attaching one or more elastic materials to at least one piece, and is discussed below in more detail.
In another aspect, the invention is directed to a composite having a creep-resistance value of about 30% or greater, specifically about 40% or greater, and particularly about 50% or greater, the composite comprising: a first piece and a second piece; at least one elastic strand or ribbon; and an adhesive composition binding at least a portion of each strand to a portion of the first piece and a portion of the second piece, the adhesive composition having a capillary-viscosity value of about 9 Pas.sec or greater and a Shore-OO-Hardness value of about 90 or greater, wherein the relative accretion value is less than about 0.1, and more particularly less than about 0.05. In some versions of the invention, the elastic strand or ribbon is not attached to a first piece and a second piece to form a composite, but instead is attached to, and enclosed by, a single piece (e.g., by folding over a portion of the single piece over the elastic strand or ribbon to form a composite).
An absorbent product having features of the present invention includes: a liquid-permeable topsheet; a liquid-impermeable backsheet attached to the topsheet; an absorbent core disposed between the topsheet and the backsheet; and a composite as described in any one of the preceding paragraphs, the composite being attached to, or an integral part of, a portion of the topsheet, a portion of the backsheet, or both. It should be understood that the composite may be attached directly, or indirectly through one or more additional pieces or components (i.e., an intermediate piece or component), to the topsheet or backsheet. One version of a method of making a composite of the present invention comprises the steps of: providing a first piece; providing a second piece; and attaching a portion of the first piece to a portion of the second piece using an adhesive composition having a capillary-viscosity value of about 7 Pas.sec or greater and a Shore-OO-Hardness value of about 65 or greater, wherein the relative accretion value is less than about 1, and more particularly less than about 0.5. In some versions of the invention, a first piece is not attached to a second piece to form a composite, but instead a single piece is provided, and this piece is folded over and attached to itself using an adhesive composition having the above-recited properties.
Another version of a method of making a composite of the present invention comprises the steps of: providing a first piece; providing a second piece; and attaching a portion of the first piece to a portion of the second piece using an adhesive composition having a capillary-viscosity value of about 9 Pas.sec or greater and a Shore-OO-Hardness value of about 90 or greater, wherein the relative accretion value is less than about 0.1, and more particularly less than about 0.05. In some versions of the invention, a first piece is not attached to a second piece to form a composite, but instead a single piece is provided, and this piece is folded over and attached to itself using an adhesive composition having the above-recited properties.
In another aspect, a method having features of the present invention comprises the steps as described in either of the two preceding paragraphs, with the additional step of ultrasonically bonding a portion of the composite (i.e., either the first piece to the second piece, or the folded-over portions of a single piece). Alternatively, or in addition to, this added step, the composite is ultrasonically bonded to a third piece, such as the topsheet, backsheet, or some other part of a disposable absorbent article, as the article is systematically built on a production line.
For example, a method of making an absorbent article or product having features of the present invention includes the steps of: providing a liquid-permeable topsheet; providing a liquid-impermeable backsheet; providing an absorbent core; providing a composite prepared by the steps outlined in one of the two paragraphs before the immediately preceding paragraph; positioning the absorbent core so that it will be between the topsheet and the backsheet in the disposable absorbent article; attaching the backsheet to the topsheet; and attaching a portion of the composite to a portion of the topsheet, a portion of the backsheet, or a portion of both.
Another version of a method of making a composite of the present invention comprises the steps of: providing a first piece; providing a second piece; providing at least one elastomeric strand or ribbon; and attaching a portion of the strand or ribbon to a portion of the first piece and a portion of the second piece using an adhesive composition having a capillary-viscosity value of about 7 Pas.sec or greater and a Shore-OO-Hardness value of about 65 or greater, wherein the relative accretion value is less than about 1, and more particularly less than about 0.5, and wherein the composite has a creep-resistance value of about 30% or greater, specifically about 40% or greater, and particularly about 50% or greater. In some versions of the invention, the elastic strand or ribbon is not attached to a first piece and a second piece to form a composite, but instead is attached to, and enclosed by, a single piece (e.g., by folding over a portion of the single piece over the elastic strand or ribbon to form a composite).
In another aspect, a method of making a composite of the present invention comprises the steps of: providing a first piece; providing a second piece; providing at least one elastomeric strand or ribbon; and attaching a portion of the strand or ribbon to a portion of the first piece and a portion of the second piece using an adhesive composition having a capillary-viscosity value of about 9 Pas.sec or greater and a Shore-OO-Hardness value of about 90 or greater, wherein the relative accretion value is less than about 0.1, and more particularly less than about 0.05, and wherein the composite has a creep-resistance value of about 30% or greater, specifically about 40% or greater, and particularly about 50% or greater. In some versions of the invention, the elastic strand or ribbon is not attached to a first piece and a second piece to form a composite, but instead is attached to, and enclosed by, a single piece (e.g., by folding over a portion of the single piece over the elastic strand or ribbon to form a composite).
In another aspect, a method having features of the present invention comprises the steps as described in either of the two preceding paragraphs, with the additional step of ultrasonically bonding a portion of the first piece to a portion of the second piece, or ultrasonically bonding the folded-over portion of a single piece. Alternatively, or in addition to, this added step, the composite is ultrasonically bonded to a third piece, such as the topsheet, backsheet, or some other part of a disposable absorbent article, as the article is systematically built on a production line.
For example, a method of making an absorbent article having features of the present invention includes the steps of: providing a liquid-permeable topsheet; providing a liquid-impermeable backsheet; providing an absorbent core; providing a composite prepared by the steps outlined in one of the two paragraphs before the immediately preceding paragraph; positioning the absorbent core so that it will be between the topsheet and the backsheet in the disposable absorbent article; attaching the backsheet to the topsheet; and attaching a portion of the composite to a portion of the topsheet, a portion of the backsheet, or a portion of both.
In another aspect, a method of making a composite or disposable absorbent article of the present invention comprises the steps of: providing a candidate adhesive composition; determining the accretion value of the candidate adhesive composition; determining the accretion value of an adhesive composition presently used to make a composite or absorbent product; and selecting the candidate adhesive composition as a substitute for the presently-used composition if the relative accretion value is less than 1, wherein the relative accretion value is determined by dividing the accretion value of the candidate adhesive composition by the accretion value of the presently-used adhesive composition.
In another aspect, a method of making a composite or an absorbent article of the present invention comprises the steps of: providing a candidate adhesive composition; measuring the capillary-viscosity value of the candidate adhesive composition; measuring the Shore-OO-Hardness value of the candidate adhesive composition; and selecting the candidate adhesive composition for use in making the composite or disposable absorbent article if the candidate adhesive has a capillary-viscosity value of about 7 Pas.sec or greater and a Shore-OO-Hardness value of about 65 or greater, and more particularly a capillary-viscosity value of about 9 Pas.sec or greater and a Shore-OO-Hardness value of about 90 or greater.
In another aspect, a method of making a composite or disposable absorbent article of the present invention comprises the steps of: providing a candidate adhesive composition; measuring the capillary-viscosity value of the candidate adhesive composition; measuring the hardness of the candidate adhesive composition; and selecting the candidate adhesive composition as a substitute for another adhesive composition used in constructing a composite or disposable absorbent article if the measured capillary-viscosity value and hardness value of the candidate adhesive composition correspond to a relative accretion value less than 1, wherein the relative accretion value is determined by dividing the accretion value of the candidate adhesive composition by the accretion value of the substituted-for adhesive composition.
These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings.